if(last_good < 0) last_good = last_contiguous;
int start_frame = MIN(last_contiguous, last_good);
start_frame = MAX(start_frame, brender_start);
if(last_good < 0) last_good = last_contiguous;
int start_frame = MIN(last_contiguous, last_good);
start_frame = MAX(start_frame, brender_start);